Precursor vapor deposited perovskite solar cells with smooth absorber layer

Abstract

Preparation of a smooth methylammoniumleadiodide (CH3NH3PbI3) perovskite absorber film is one of the most critical processes in fabricating a perovskite photovoltaic cell with high efficiency. In this study, we report an original coating method to prepare CH3NH3PbI3 films by using the solvent vapors of precursor methylamine (MA) and hydroiodic acid (HI) solutions on lead (II) iodide (PbI2) thin films. In this strategy, the vapors of MA and HI solutions were briefly treated to the PbI2 coated substrate and then the resultant film was annealed to obtain smooth perovskite thin layer. After the topographic analyses of the thin films, the surface roughnesses of the perovskite films were found to be limited by the surface roughnesses of the PbI2 films before precursor vapor exposure. Another important aspect of our approach is that there is no need to synthesize methylammonium iodide (CH3NH3I) salt for active layer preparation. Furthermore, this method enables large-area fabrication of high quality films by a very simple and brief process. After the characterization of preliminary devices with this method, we obtained a short circuit current density of 14.67 mA/cm2, an open circuit voltage of 0.815 V, a fill-factor of 0.59, and a power conversion efficiency of 7.08%.